Liquid crystal display devices are mainly used in monitors of televisions and personal computers, and mobile appliances such as smart phones. Examples of the liquid crystal display mode include twisted nematic (TN) mode, super twisted nematic (STN) mode, and vertical alignment (VA) mode, in-plane-switching (IPS) mode, and fringe field switching (FFS) mode that use thin film transistors (TFTs). There are three main properties desired for the liquid crystal display devices: (1) high-speed response, (2) low drive voltage, and (3) a wide operation temperature range with room temperature at the center. Another is (4) high reliability in an operation environment under light or heat.
Roughly speaking, a liquid crystal composition is required to have the following properties in order to satisfy the respective properties (1) to (3) above: (a) low viscosity (η), (b) a large absolute value of dielectric anisotropy (Δε), and (c) a high nematic phase-isotropic liquid phase transition temperature (Tni) (PTL 1). Furthermore, the refractive index anisotropy (Δn) must be adjusted to be within an appropriate range for the cell gap. In order to satisfy the property (4) described above (in order to enhance reliability of the liquid crystal display device), the liquid crystal composition is also required to be stable against external stimuli such as light, heat, moisture, and air (d).